A Multiple Conjunction is a kind of aspect configuration in which 3 or more planets are all in conjunction with each other. These planets are typically (though not always) in the same sign.
Every planet in the group must be within orb of conjunction with all other planets in the group. In other words, the planets that are farthest apart must still be within orb of conjoining each other.
This collection of planetary energies is very powerful and complex. This is not merely a merging of two planetary forces, as with a standard conjunction – this is a very intense merging of diverse energies which carry a powerful vortex of energy in the chart. The effects will vary depending on the planets, sign and house involved.
Someone who was born with a Multiple Conjunction can seem like they were born under the sign where the Conjunction takes place, even if the Sun is not one of the conjunct planets. A massive amount of that person's personality, style and perspective is focused within the sign of the conjunction.
Typically, there is a struggle to find ways to bring all of the planets into cooperative harmony. The overall effect tends to be very creative (in terms of artistry, innovation or originality), although it can be a challenge to harness all the planets at once – a lilttle like herding cats. As with the usual 2-planet conjunction, this is tricky because each planet is striving to express its own nature; yet it is continually being modified and reshaped by the other planets. As a result, one planet will often become more dominant, and the others more in the background, depending on its strength, dignity and rulership.
